The present invention is related to tip clearance measurement systems, and in particular to radio frequency circuitry employed in tip clearance measurement systems.
Tip clearance measurement systems are utilized to measure the turbine blade tip clearance in aircraft engines. Tip clearance refers to a distance between rotating components (such as turbine and/or compressor blades) and stationary components (such as a turbine case). Efficiency of aircraft engines is increased by minimizing the distance between these rotating and stationary components. In some cases, the distance can be controlled by selectively heating/cooling the stationary case. The case is expanded/contracted based on the heating/cooling provided, and the distance is minimized.
Tip clearance measurement systems provide feedback regarding the distance between rotating and stationary components. A typical tip clearance measurement system uses a probe to direct electromagnetic (EM) waves toward the turbine blade. In addition, the probe monitors the reflection of the EM waves (as they reflect off of the turbine blades) and uses the monitored reflections to determine the distance between the blade tips and the stationary case. The EM waves are generated at specific frequencies (e.g., microwave, radio frequencies). At least two difference frequencies are required, including a reference frequency and a main frequency. Typically, separate circuits are required to condition and provide each of these frequencies to the probe. In addition, separate circuits are required for each frequency to analyze the reflected signals received from the probe.